@nikonstantinou Hi, I checked it and these values are contained in the original data.
We use the following source: "OSCAR third degree resolution ocean surface currents".
Link: https://podaac.jpl.nasa.gov/dataset/OSCAR_L4_OC_third-deg
It is analysis which is calculated once per 5 days. The actual one is from the 17th of April.
Sea currents is not our major feature, but if you have a tip/link to better data, please share it and we will consider replacement of the data source (maybe there is available even forecast).

The OSCAR source data is provided in a 20NM grid and typically has gaps at coastlines and in shallow bank areas. @meteo-GR, I think you are right - that the interpolation in windy.com visualization is creating artifacts that are not supported by the source data. See the comparison below: